The present invention relates to a caster assembly for a use with furniture, and, more particularly, to a caster assembly adapted for use with a wooden or plastic leg of a piece of furniture.
In general, there are many types of furniture casters that are available and which are affixed or incorporated into the legs of such furniture to enable that particular piece of furniture to be readily rolled from one location to another.
Accordingly, the caster assemblies for furniture normally have rotatable rollers to facilitate the movement of the furniture. Such caster assemblies also generally have an elongated stem that interfits into the furniture. That stem has a central longitudinal axis along which is directed the weight of the furniture The roller itself is mounted to the assembly within a housing and the roller is rotatably mounted to that housing to roll about a central axis that is parallel to the plane of the floor. The housing is also pivotally mounted to the furniture leg so that the roller itself can not only rotate about its axis, but the housing, including the roller itself, can also pivot 360 degrees about the main longitudinal axis of the stem.
The swiveling action or movement is necessary to correctly align the roller for movement in the proper direction, however, such swiveling movement can be generally difficult to accomplish. For one reason it is apparent that all of the rollers supporting the furniture must be correctly aligned in order to easily move the furniture. In most instances, the rollers are positioned in various directions and it is therefore necessary to align all of the rollers at the initial movement of the furniture. With the weight of many pieces of furniture, there is considerable friction acting against the swiveling action of the caster assembly and the problem is aggravated by the need to align some 4-5 rollers in order to roll the furniture. Additionally, the roller is often embedded into an indentation in the carpet that lies along the surface of the roller and the roller must be moved out of the indentation to swivel. As such, therefore, while the swivel action is necessary to properly move the furniture, it can be somewhat difficult to get the swivel action to operate easily and thus the initial movement of the furniture is not easy to accomplish, particularly when the piece of furniture is on carpeting with padding.
The typical conventional caster for use with carpet is a cylindrical member that contacts the floor at a certain finite distance away from the longitudinal, vertical axis of the stem so that the roller can pivot to a position determined by the direction the furniture is being moved and then the roller rotates to make that movement easy to accomplish. A typical roller caster assembly used on a bed frame is shown and described in U.S. Pat. No. 4,007,502 of Mis. As can be seen in the Mis patent, the roller is offset with respect to the downward force that acts through a stem and, as will become clear, this typical caster of Mis suffers from certain inherent weaknesses.
Thus, since the contact point between the roller and the floor is located at an offset dimension from the longitudinal, vertical axis of the stem along which the weight of the furniture is directed, a bending moment is created based on the weight of the furniture acting downwardly on the stem and the distance between the location of that force along the longitudinal axis of the stem and the point where the roller contacts the floor to support the frame.
One of the difficulties with such casters, therefore, is that the bending moment created by that offset creates stress on the caster assembly and can cause a premature failure of the caster assembly or the furniture itself, thereby disabling the entire unit. The problem is aggravated, of course, with legs having increased degrees of weakness, and in particular, with the use of plastic legs as shown and described in U.S. Pat. No. 3,828,376 of Miller. Accordingly, it would be advantageous to have a caster assembly that has rollers that provide better support for the furniture and which do away with the offset that causes the bending moment and the premature fracture of essential components such as the leg of the furniture, thus avoid damaging the furniture. There are rollers that have ball bearings that may aid in the swiveling of the roller or aid in the rolling motion of the roller itself but most require the offset and the consequent swiveling action to operate in moving the furniture.
Other prior art furniture support assemblies have, in fact, utilized a plurality of elements that contact the floor and examples are illustrated in U.S. Pat. No. 1,060,076 of Glowacki and U.S. Pat. No. 1,282,396 of Friend. In the aforementioned patents, however, while a plurality of members contact the floor and thus allow the weight to be borne by a plurality of elements, there is a further problem with respect to the ease of moving such casters as the spherical members are clamped into the housing supporting the particular piece of furniture and the spherical contact members do not thus freely rotate to allow the ready movement of the furniture. Accordingly, in Glowacki, the balls that actually contact the floor are clamped tightly into a circular dome and thus are not movable with respect to the dome as the furniture is moved. Therefore, while the prior art did consider the support of the weight of a piece of furniture on a plurality of contact members, the moving of the furniture was not enhanced and only the idea of a strong support was considered and appreciated.
In addition to caster assemblies, there are also glide assemblies that are mounted to the various pieces of furniture and have a generally flat, planar bottom contacting the floor. The glide assemblies are preferably used where the furniture is located on a hard or slippery surface such as a wood or tile floor and thus the flat bottom does not easily slip or cause damage to the floor itself. With such flooring surfaces, the user of a caster having a roller causes unnecessary sliding or rolling as contrasted to the intended use of a rug roller or caster on a carpeted surface where the friction with the carpet reduces the mobility of the roller or caster.
Glide assemblies are inherently stronger than caster assemblies since the weight of the bed frame using a glide acts along the longitudinal axis of the glide directly to the point of contact with the floor, and thus, there is no offset from that axis to the point of contact and, hence, no bending moment. In addition, of course, the glide planar surface allows more surface contact with the floor and thus carries the weight of the furniture over a wider area so as to provide a better distribution of that weight. As such, the glide assembly has enhanced strength and stability over the caster assembly.
A further alternative is with the use of a caster cup that is generally cup shaped that is slid underneath a roller of a caster assemble to aid in slowing the mobility of the caster and to stabilize the piece of furniture, particularly when used on a slippery flooring surface. The caster cups, however, are easily displaced from under the roller since they are not firmly locked to or attached to the caster assemblies and are thus difficult to maintain in place when the furniture is moved during the normal use of the furniture. Thus, over time, the caster cups become displaced with respect to the roller and no longer serve their intended purpose.
As a further problem with many of the aforedescribed caster assemblies, since the caster roller needs to pivot 360 degrees about its vertical axis, it is very difficult to build the caster assembly into a wooden or plastic leg of the furniture and, therefore, the caster for a wooden or plastic leg is simply screwed into the bottom of a leg by means of a threaded stem and, accordingly, creates a weak point as well as a less than pleasing appearance of the caster affixed to the bottom of a leg.
Accordingly, it would be advantageous to have a caster assembly that can be used with a wooden or plastic furniture leg that can be recessed into the leg so that the overall appearance is pleasing and the caster fits in with the exterior contour of the leg. It would also be advantageous to have a caster assembly for a wooden or plastic furniture leg wherein the caster assembly has a strong connection to the furniture leg and where there is no upstanding stem or other member that can introduce a weak point into the leg/caster combination. It would be still further advantageous to have a caster assembly for a wooden or plastic furniture leg where there is a glide that can be removably affixed to the bottom of the caster so that the user can readily convert the caster to a glide and vice versa.